Stations Heard (was Re: [AMRadio] FS: Bogen)


W5OMR/Geoff w5omr at satx.rr.com
Thu Jul 27 09:39:11 EDT 2006


John E. Coleman (ARS WA5BXO) wrote:
> Mine used to run some of those tubes but I modified it to use some vertical output tubes from the TV repair days.  The speech amp is not required to deliver any power to the modulator as the modulator is AB1 and even in the days when I once needed more audio and ran the modulator AB2 the solid state driver did all the work of grid current.  The plates of the Bogen output tubes or capacitively coupled to the grids of the four 813s and a center tapped choke feed the bias to the grids

Needless to say, that rig sounds good, when it's on the air.

I need to see what I can do, to secure a remote transmitting site, for 
my rig.  This latest road-trip has afforded me the opportunity to listen 
to some of the late-night operation that occurs on 3.880 and 3.885 
(where the bug-catcher is tuned) and I'm hearing -BIG- signals from the 
likes of K4KYV (good to hear you on 75m again, Don!), W5JO and welcome 
back to the airwaves, Brian/W5AMI.  That Flex radio with the Henry amp 
is a killer combination from North Central Arkansas!  Can't wait to hear 
how it's going to sound on 40m today, at 11:00am, CST, on 7.200Mc.  Rest 
assured, as good as you say my mobile signal was last night, that 
antenna works -so- much better on 40m.  I grow anxious in anticipation.

I need to get back on during the evening hours, but being besieged with 
'neighborhooditis', I don't dare fire up even a 200w signal from the 
homebrew rig, less I envoke the nightmares of the neighbors coming down 
the street with a bucket of hot tar, a sack full of feathers and a noose 
for which to hang me from the yard-arm on my tower!  ;-)

Don, and John (and all the rest of us 'technically minded individuals') 
While it might be a bit late in the game to petition the ARRL for a 
change to the Radio Amateurs Handbook, I wonder if it's worth pursuing 
having the book changed.  Because, while it's true that to modulate an 
AM carrier to 100% with a sine-wave, you only need 50% of the total 
final output power in the modulator, the same can -not- be said for 
'voice' modulation of the same carrier.  Meaning, if you had a 1000w 
carrier, in oder to modulate it to 100% wiht a sine-wave, you only need 
500w of audio power.  But, as evidenced by the research and development 
by WA5BXO, K4KYV, WA3WDR and W5TOB, when modulating the carrier with 
complex voice patterns, one needs to have, typically, 4x the amount of 
power available in the modulator than the carrier presented.  This 
allows for the natural asymmetrical peaks in typical voice 
characteristics to fully modulate the carrier, without flat-topping 
causing splatter, distortion and buckshot up and down the band.

If you're unfamiliar with what I'm speaking of, check out 
http://w5omr.shacknet.nu:81/~wa5bxo/asyam/Amplitude%20Modulation.htm or 
http://www.qsl.net/wa5bxo/asyam/aam3.html

Anyway, with the influx of 'new-to-AM' hams, by digging in the 
handbooks, what little information there is on AM does not include 
anything of the likes, as what's discussed in the website(s) mentioned 
above.

The rain has finally let up a bit here in Baton Rouge, LA.  I'm hoping 
for good conditions on 40m late this morning.

-- 
Driving your AM Rig without a scope, 
is like driving your car at night, without headlights. (K4KYV)

--
73 = Best Regards,
-Geoff/W5OMR





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